This invention relates to the bleaching of certain triarylmethane dyes in solution with low concentrations of hypochlorite ion, activated by the combination of bromide ion and ammonium ion. In particularly preferred embodiments, the invention relates to methods, compositions and articles for automatically cleaning and sanitizing toilets wherein a dye/activator composition and hypochlorite are separately dispensed into the toilet bowl during flushing. The water in the bowl at the end of the flush is colored by the dye. However, within a relatively short period of time after the flush, the dye is oxidized to a colorless state thereby providing a visual signal that the hypochlorite sanitizing agent is present and "acting" in the bowl.
Automatically dispensed toilet bowl cleaning and/or sanitizing products, which contain dyes to provide a visual signal to the user that product is being dispensed, are well known. Such products are sold in the United States under the brand names VANISH AUTOMATIC (Drackett Products), TY-D-BOL AUTOMATIC (Knomark, Inc.) and SANIFLUSH AUTOMATIC (Boyle-Midway). None of these products contains a hypochlorite sanitizing agent and all of them provide a color to the bowl water which persists between flushing. U.S. Pat. No. 3,504,384, Radley et al., issued Apr. 7, 1970, discloses a dual compartment dispenser for automatically dispensing a hypochlorite solution and a surfactant/dye solution to the toilet bowl during flushing. The dye which is taught in the patent is Disulfide Blue VN150. It is believed that the dye referred to in Radley et al. is actually Disulphine Blue VN150 (Color Index No. 42045). (The abbreviation "C.I." will be used hereinafter to designate "Color Index.") This dye has been reported in U.S. Pat. No. 4,248,827, Kitko, issued Feb. 3, 1981 to be quite resistant to oxidation to a colorless state by hypochlorite; thus, it too provides a persistent color to the toilet bowl water, even in the presence of the hypochlorite.
A persistent color in the toilet bowl water has certain attendant negatives. The dye can cause staining of the toilet bowl itself or of deposits (such as water hardness deposits) which accumulate on the surfaces of the bowl between manual cleanings. Also, a persistent colored solution in the bowl will tend to obscure medical symptoms such as the passing of blood during excretion or urination. Further, a persistent color in the toilet bowl water tends to obscure otherwise visible evidence of soiling on surfaces of the toilet bowl which are below the water line.
U.S. Pat. No. 4,248,827 supra discloses certain dyes which are bleached to a colorless state in less than 10 minutes in the toilet bowl by low concentrations of hypochlorite or hypochlorite which is catalyzed by bromide ion. Among these is the triarylmethane dye Acid Green 2G (C.I. No. 42085). In this dye there are no substituents on the aryl rings in the positions which are ortho to the ring carbon which is attached to the methane carbon. U.S. Pat. No. 4,248,827 also discloses certain triarylmethane dyes which are not bleached to a colorless state within the stated 10 minute period by hypochlorite or hypochlorite/bromide. These are FD and C Blue No. 1 (C.I. No. 42090), FD and C Green No. 3 (C.I. No. 42053) and Disulphine Blue VN (C.I. No. 42045). All of these triarylmethane dyes have a substituent group in the ortho position on one of the aryl rings attached to the methane carbon.
An object of the present invention is to provide a method for bleaching aqueous solutions of triarylmethane dyes which have a substituent in the ortho position of at least one of the aryl rings attached to the methane carbon, with low concentrations of hypochlorite ion.
Another object of the invention is to provide a method for automatic cleaning and sanitization of toilets wherein a visual color signal is provided to indicate that the sanitizing agent is present and acting in the toilet bowl, and to provide articles and compositions adapted for use in said method.
Another object of the invention is to provide a visual color signal which persists in the toilet bowl for a relatively short time after flushing.
Another object of the invention is to provide, by a visual color signal, a means by which the consumer will know when a new supply of sanitizing agent needs to be provided for the toilet.